Hello, vivrenfr! The problem with this word "well" is that it's a bit ambiguous. "Well" on its own normally means "en bonne santé". If you say, "She's well", generally that would mean, "Elle est en bonne santé", "Elle s'est remise d'une maladie," etc. If someone has been ill and now they've recovered, we'd say, "He's well now."

So, if your sentence said, "She's well, apart from feeling very tired," for me that would imply that she has been sick; now she's much better, though she still feels very tired.

Whereas "She's quite well, apart from feeling very tired," doesn't necessarily mean that she's been sick. She could have been sick. But she could, for example, be pregnant, and it's her pregnancy that is making her tired. Apart from that, everything's OK.

So, this is difficult to explain, and I don't know if I'm helping you. I may just be confusing you, because our use of "well" and "quite/very well" aren't consistent. Also, there are exceptions to the rules I've given above.